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Hi all,

 

I recently acquired the below fossil, a pair of articulated jaws, purportedly from Pachystropheus rhaeticus, still with teeth, found at Garden Cliff/Westbury-on-Severn. Whether I wasn't paying proper attention when I bought it or just hoping there wouldn't be any pyrite on the piece, when I received the specimen it turned out that there are quite numerous pyrite-crystals growing to the side of the fossil. As it's quite an unusual piece that I'd rather like to keep, I'm now looking for people with experience with pyrite from the Garden Cliff location. In essence, I'd like to ask how stable the pyrite from this location typically is: whether it decays into a black oxidation product or starts blooming with time. How concerned should I be about the stability of this piece? The pyrite itself looks relatively clean right now, so I'm thinking the rock on which the fossil sits hadn't been exposed for too long. But any advice would be welcome.

 

305630106_PachystropheusrhaeticusarticulatedjawswithteethandvertebraeGardenCliffGloucester01.thumb.jpg.4ed8928344f7e08a2e86e10aba2db99b.jpg1413883152_PachystropheusrhaeticusarticulatedjawswithteethandvertebraeGardenCliffGloucester02.thumb.jpg.70e565bd2e80d0b138b1853d12f1accc.jpg1644336205_PachystropheusrhaeticusarticulatedjawswithteethandvertebraeGardenCliffGloucester03.thumb.jpg.eadec20fedc4d114773bc3be7641a805.jpg1116859829_PachystropheusrhaeticusarticulatedjawswithteethandvertebraeGardenCliffGloucester04.thumb.jpg.d97cc9659a50c24dd037d1d15929f6b2.jpg

 

@Welsh Wizard @Pterygotus @DanJeavs

Edited by pachy-pleuro-whatnot-odon

'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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Hi

 

The pyrite seems stable. I’ve pieces that show no sign of decay and I’ve not treated them.

 

I think these are fish jaws. I did look at them when they were for sale. There have been no identified pachystropheus jaws that I’m aware of but you would expect to find them in the formation. In this case, the teeth do look like fish teeth. It would be good if they were pachystropheus.

 

Nick

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7 hours ago, Welsh Wizard said:

Hi

 

The pyrite seems stable. I’ve pieces that show no sign of decay and I’ve not treated them.

 

I think these are fish jaws. I did look at them when they were for sale. There have been no identified pachystropheus jaws that I’m aware of but you would expect to find them in the formation. In this case, the teeth do look like fish teeth. It would be good if they were pachystropheus.

 

Nick

 

Thanks, Nick! Yeah, that's what I was afraid of too, though I'm not familiar enough with either fish bone or teeth (certainly not from the location) to confidently draw this conclusion myself. The fact that no jaw fragments have been identified so far as belonging to Pachystropheus (thus, llittle chance then, I guess, of finding an illustrated specimen in the book "Fossils of the Rhaetian Penarth Group" I'm still expecting :() seems to further reduce the likelihood of these remains actually belonging to that animal, as does the fact that these are apparently not the first specimens the vendor had sold as such. In took a chance, and it's a nice set of jaws either way, but it's good to have confirmation of my suspicion that this specimen is likely to be fish. I was actually hesitating to express this uncertainty in the wording of my original post, but decided not to in the end, a situation I have since remedied.

 

Indeed, if Pachystropheus is to be considered a choristodere, one may expect its jaw and teeth to look somewhat similar to that of Cteniogenys antiquus below (source). I was hoping my specimen could simply be a lingual view on such a jaw...

 

Cteniogenys_dentary.thumb.jpg.8fd5e225d2cc54cf9f610161f40482bc.jpg

 

In any case, it's good to know that the pyrite on this piece will likely remain stable (the original advertisement for it even mentions coating with a mat veneer, which may help reduce chances of decay - although opinions on this differ, of course). That's quite a relief!

Edited by pachy-pleuro-whatnot-odon

'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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I suspect the skull elements of pachystropheus were quite delicate.

 

Its worth noting that a lot of westbury rhaetic material can be classed as associated and it is a big assumption to assume they are from the same animal and I’ve seen very little articulated material. The articulated stuff tends to be vertebrae but only maybe two together. It’s easy to assume that bones are together until you uncover them and they are not. With that in mind, it fascinates me what can be found in these formations.
 

Hope this helps

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32 minutes ago, Welsh Wizard said:

I suspect the skull elements of pachystropheus were quite delicate.

 

Yes, that seems a reasonable explanation. Skull bones, in general, are, of course, very thin and fragile, and in the case of Pachystropheus I understand that bones from hands and feet are also very rare finds. That having been said, it would be interesting to check  whether such small and fragile bones as we may expect a Pachystropheus-skull to have consisted of would be present in the deposit, whether from Pachystropheus, other or unidentified species, in order to in investigate whether we might indeed be dealing with a preservational bias. For, in any case, you would all the same expect to find Pachystropheus-teeth, even if only isolated specimens. But I don't believe these have been reported either...? Then again, without clear association with jaws that can unmistakably be attributed to Pachystropheus, it'd be very difficult to identify such teeth for what they are...

 

Interestingly, I've once been shown a big slab of Westbury bonebed per photograph that was absolutely packed with Pachystropheus remains, including the much rarer hand and foot bones. This block also contained a jaw that the original finder and current owner of the block described as fish jaw, but that to me, from what I could see, superficially looks like the Cteniogenys-jaw I mentioned above. In fact, my first impression was that it might be some sort of small crocodile jaw. So, who knows, may be a jaw is still out there to be found, just way less likely to be collected or show up in a public venue as every Pachystropheus, of course, had many vertebrae but only two mandibles ;)

 

(alternatively, the same thing may be going on with Pachystropheus-skulls as with plesiosaur skulls, against which, I've been told, a preservational bias exists due to their skulls not having been fully calcified)

 

Quote

Its worth noting that a lot of westbury rhaetic material can be classed as associated and it is a big assumption to assume they are from the same animal and I’ve seen very little articulated material. The articulated stuff tends to be vertebrae but only maybe two together. It’s easy to assume that bones are together until you uncover them and they are not. With that in mind, it fascinates me what can be found in these formations.

 

Funny you should mention that. I just replied the same thing in a different thread earlier today ;)

Notwithstanding, I do agree this is probably what the seller of my piece based their identification if the jaws upon...

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'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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Not seen the other thread.

 

I suspect I know what block you are talking about re pachystropheus bones.

 

There appears to have been some sort of separation effect in the westbury formation. Similar to when you shake a cereal box and the big and small pieces separate. There also seems to be a mix of pristine and worn/rotten bones.

 

Who knows. The more people look and the more time people spend preparing (as opposed to bashing) the blocks, then the higher probability of finding really interesting things. Trouble is, people like to find ichthyosaur and plesiosaur verts and ignore other stuff. 
 

Here’s a small humerus I found, probably reptile (not pachystropheus) from Aust. It’s about 5 mm long.

 

7815F4A0-4624-4941-8DCD-D802A7E37F9D.thumb.jpeg.53c7c78745a0423f6e2b33a96619f7a2.jpeg

 

 

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2 hours ago, Welsh Wizard said:

Not seen the other thread.

 

It's quite an old one, so I don't think it would really have stood it. But I happened across it and thought I could add my 2ct since the conclusion of the thread didn't seem satisfactory. Anyway, it doesn't really have any pertinence to the current thread, other than like localities and the fact that I used a similar line of argument there, advocating care in not assuming bone material to be associate...

 

2 hours ago, Welsh Wizard said:

I suspect I know what block you are talking about re pachystropheus bones.

 

Quite possible. I can't imagine too many other blocks like it going around ;)

 

2 hours ago, Welsh Wizard said:

There appears to have been some sort of separation effect in the westbury formation. Similar to when you shake a cereal box and the big and small pieces separate. There also seems to be a mix of pristine and worn/rotten bones.

 

That's both peculiar and interesting, I hadn't heard of that before. If so, then there'd indeed seem to be a preservational bias towards larger, more solid bone. Do you know what palaeoenvironment they reconstructed for the formation? Sounds like it'd need to be an environment with two primary types of waves - one to bring in all bone material and collate it, the other to sort the smaller and lighter stuff out - as well as one that would occasionally fall dry altogether to allow the bone to rot and explain the oxidizing iron stains in the sandstone matrix... Probably something like a lagoon, in which the main tide would wash in and trap trap what would become the fossils, while the secondary one would afterwards displace the smaller material? If the lagoon would occasionally dry up, as, for instance in summer, this may explain why certain bones appear more worn than others. It may also help explain the terrestrial component found in the formation. Just speculating here, though...

 

2 hours ago, Welsh Wizard said:

Who knows. The more people look and the more time people spend preparing (as opposed to bashing) the blocks, then the higher probability of finding really interesting things. Trouble is, people like to find ichthyosaur and plesiosaur verts and ignore other stuff. 

 

What probably doesn't really help either is that I understand this material not being exactly easy to prepare, with the best method, as I've been told, being acid preparation - a method for which most people would likely have means nor patience :unsure:

 

2 hours ago, Welsh Wizard said:

Here’s a small humerus I found, probably reptile (not pachystropheus) from Aust. It’s about 5 mm long.

 

7815F4A0-4624-4941-8DCD-D802A7E37F9D.thumb.jpeg.53c7c78745a0423f6e2b33a96619f7a2.jpeg

 

Wow, that's an interesting specimen! Nice find! You do need to keep your eyes out for these, though, as fossils like this are easily missed for their size - and as you said, lack of public appeal. Along those lines I once found a tiny fragment of Saurorhynchus sp. jaw, still with the teeth in place, on a piece of shale from Holzmaden. I didn't discover it until quite late, however, as I had originally picked the rock up for an unusual imprint that turned out to be the remains of an ammonite stuck in the rock vertically rather than the usual horizontally. It was only when breaking the rock down for disposal that I noticed the jaw... Most people likely wouldn't have spotted it :look:

'There's nothing like millions of years of really frustrating trial and error to give a species moral fibre and, in some cases, backbone' -- Terry Pratchett

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